Spurious hypophosphatemia in a patient with multiple myeloma.

We report a patient with multiple myeloma and a prolonged history of hypophosphatemia who had remained asymptomatic. Extensive evaluation for a cause, including the search for a renal tubular disorder, oncogenous osteomalacia, or a parathyroid hormone (PTH)-related protein was unproductive. Renal biopsy showed no evidence of myeloma kidney.

Lipoprotein lipase reduces secretion of apolipoprotein E from macrophages.

Macrophages are a significant source of lipoprotein lipase (LPL) and apolipoprotein E (apo E) in the developing arterial wall lesion, and each of these proteins can importantly modulate lipid and lipoprotein metabolism by arterial wall cells. LPL and apo E share a number of cell surface binding sites, including proteoglycans, and we have previously shown that proteoglycans are important for modulating net secretion of apoprotein E from macrophages. We therefore evaluated a potential role for LPL in modulating net secretion of macrophage-derived apo E.

Acute dyslipoproteinemia induced by interleukin-2: lecithin:cholesteryl acyltransferase, lipoprotein lipase, and hepatic lipase deficiencies.

Recombinant human interleukin-2 (rIL-2) is used to treat refractory cancers. During such treatment, patients develop severe hypocholesterolemia along with striking alterations in the concentration and composition of the circulating lipoproteins. The present study was undertaken to gather information about the pathogenesis of these abnormalities.

Evidence for sex steroid inhibition of lipoprotein lipase in men: comparison of abdominal and femoral adipose tissue.

Plasma estradiol has been suggested to suppress adipose tissue lipoprotein lipase (LPL) activity in women. The present study explores the regulation of LPL by sex steroids in sedentary obese men (N = 24) at their usual weight. Femoral adipose tissue LPL activity, eluted with serum and heparin or extracted with detergent, showed significant inverse correlations with plasma levels of testosterone, bioavailable testosterone, dihydrotestosterone, and estradiol.

Increased lipase inhibition in uremia: identification of pre-beta-HDL as a major inhibitor in normal and uremic plasma.

The hypertriglyceridemia commonly observed in uremia has been attributed to an abnormally high inhibitor activity in plasma for lipoprotein lipase (LPL) and hepatic lipase (HL), both of which have a key role in lipoprotein metabolism. The purpose of this investigation was to establish a relationship between plasma lipase inhibitor activity and hypertriglyceridemia, identify the main plasma lipase inhibitor, and determine the basis for the greater inhibitor activity in uremia. In a mixed population of normal (N = 8) and uremic subjects (N = 12), log-transformed plasma triglycerides correlated with both inhibitor activity and uremic status.

Cellular catabolism of normal very low density lipoproteins via the low density lipoprotein receptor-related protein/alpha 2-macroglobulin receptor is induced by the C-terminal domain of lipoprotein lipase.

Lipoprotein lipase (LPL) binds to the low density lipoprotein receptor-related protein (LRP)/alpha 2-macroglobulin receptor and induces catabolism of normal human very low density lipoproteins (VLDL) via LRP in vitro. Recent studies showed that the C-terminal domain of LPL can bind LRP in solid phase assays and inhibit cellular catabolism of two LRP ligands, activated alpha 2-macroglobulin and the 39-kDa receptor-associated protein (Williams, S.E.

The carboxyl-terminal domain of lipoprotein lipase binds to the low density lipoprotein receptor-related protein/alpha 2-macroglobulin receptor (LRP) and mediates binding of normal very low density lipoproteins to LRP.

Lipoprotein lipase (LPL) binds with high affinity to the low density lipoprotein receptor-related protein/alpha 2-macroglobulin receptor (LRP) and promotes binding, uptake, and degradation of normal triglyceride-rich lipoproteins in a process mediated by LRP (Chappell, D. A., Fry, G.

Lipoprotein lipase induces catabolism of normal triglyceride-rich lipoproteins via the low density lipoprotein receptor-related protein/alpha 2-macroglobulin receptor in vitro. A process facilitated by cell-surface proteoglycans.

Bovine milk lipoprotein lipase (LPL) induced binding, uptake, and degradation of 125I-labeled normal human triglyceride-rich lipoproteins by cultured mutant fibroblasts lacking LDL receptors. The induction was dose-dependent and occurred whether LPL and 125I-lipoproteins were added to incubation media simultaneously or LPL was allowed to bind to cell surfaces, and unbound LPL was removed by washing prior to the assay. Lipolytic modification of lipoproteins did not appear to be necessary for increased catabolism because the effect of LPL was not prevented by inhibitors of LPL's enzymatic activity, p-nitrophenyl N-dodecylcarbamate or phenylmethylsulfonyl fluoride.

Mutations in exon 3 of the lipoprotein lipase gene segregating in a family with hypertriglyceridemia, pancreatitis, and non-insulin-dependent diabetes.

A proband with chylomicronemia, pancreatitis, and non-insulin-dependent diabetes (NIDDM) bears two different mutations in exon 3 of the lipoprotein lipase (LPL) gene: a missense mutation, 75Arg-->Ser, inherited through the paternal line and a truncation, 73Tyr-->Ter, through the maternal line. NIDDM appeared to be independently segregating. The R75S mutant was studied in extracts and media from transfected COS-1 cells.

Hypoalphalipoproteinemia: postprandial response of subjects with preprandial normotriglyceridemia and hypertriglyceridemia to various diets.

The effect of a single oral fat meal (60 g fat/m2 body surface area) enriched in either saturated (SFA) or polyunsaturated ([PUFA] omega-6 or omega-3) fatty acids on postprandial lipoprotein levels was studied in four men with primary hypoalphalipoproteinemia (HP) and in four age- and sex-matched controls. Vitamin A was included in the meal to label intestinally derived triglyceride-rich particles (TRP) with retinyl palmitate (RP). The HP subjects were either mildly hypertriglyceridemic (group A) or normotriglyceridemic (group B) and were phenotyped for post-heparin lipoprotein lipase (LPL) and hepatic triglyceride lipase (HTGL) activities and apolipoprotein (apo) E isoforms.

The low density lipoprotein receptor-related protein/alpha 2-macroglobulin receptor binds and mediates catabolism of bovine milk lipoprotein lipase.

Lipoprotein lipase (LPL), the major lipolytic enzyme involved in the conversion of triglyceride-rich lipoproteins to remnants, was found to compete with binding of activated alpha 2-macroglobulin (alpha 2M*) to the low density lipoprotein receptor-related protein (LRP)/alpha 2-macroglobulin receptor. Bovine milk LPL displaced both 125I-labeled alpha 2M* and 39-kDa alpha 2M receptor-associated protein (RAP) from the surface of cultured mutant fibroblasts lacking LDL receptors with apparent KI values at 4 degrees C of 6.8 and 30 nM, respectively.

Missense mutations in exon 5 of the human lipoprotein lipase gene. Inactivation correlates with loss of dimerization.

Most missense mutations of the lipoprotein lipase (LPL) gene identified among LPL-deficient subjects cluster in a segment of the sequence that encodes the catalytic triad as well as functional elements involved in the activation of the lipase at lipid-water interfaces. Consequently, loss of activity may result either from direct alterations of such functional elements or from less specific effects on protein folding and stability. This issue was addressed by examining biochemical properties of four such variants (A176T, G188E, G195E, and S244T) in a heterologous expression system (COS-1 cells).

Role of basal triglyceride and high density lipoprotein in determination of postprandial lipid and lipoprotein responses.

The present study reports on the interaction between basal triglyceride and high density lipoprotein (HDL) cholesterol in determining the magnitude of postprandial triglyceridemia. The vitamin A fat-loading test was used to label intestinally derived triglyceride-rich particles after a high fat meal in 18 subjects with low HDL cholesterol and 6 control subjects who had normal fasting triglyceride and HDL cholesterol levels. The patients with low HDL cholesterol were divided into 2 groups on the basis of their basal triglyceride concentrations; 11 had normal triglyceride levels, and 7 had elevated serum triglycerides (HTG).

Successful hyperlipemic pregnancy.

Women with hypertriglyceridemia are prone to gestational pancreatitis, a condition carrying substantial maternal and fetal risk. We describe a 33-year-old woman with familial hypertriglyceridemia who had recurrent hyperlipidemic abdominal crises during previous pregnancies despite dietary fat restrictions. A fifth pregnancy was carried to term without complications after aggressive dietary therapy and intermittent intravenous feeding, administered whenever her triglyceride levels exceeded an arbitrarily selected threshold concentration of 28 mmol/L.

Fasting hypertriglyceridemia in noninsulin-dependent diabetes mellitus is an important predictor of postprandial lipid and lipoprotein abnormalities.

Postprandial lipoprotein metabolism may be important in atherogenesis and has not been studied in detail in noninsulin-dependent diabetes mellitus (NIDDM). We used the vitamin A fat-loading test to label triglyceride-rich lipoprotein particles of intestinal origin after ingestion of a high fat mixed meal containing 60 g fat/m2 and 60,000 U vitamin A/m2 in 12 untreated NIDDM subjects with normotriglyceridemia (NTG; triglycerides, less than 1.7 mmol/L), 7 untreated NIDDM subjects with moderate hypertriglyceridemia (HTG; triglycerides, 1.

Postprandial lipoprotein metabolism in normal and obese subjects: comparison after the vitamin A fat-loading test.

Abnormalities in fasting lipid and lipoprotein levels are known to occur in obesity and other hyperinsulinemic states. However, postprandial lipoprotein metabolism has not been studied systematically in obese subjects using sensitive techniques to distinguish between triglyceride-rich lipoprotein particles derived from the intestine and the liver. In the present study the vitamin A fat-loading test was used to label intestinally derived triglyceride-rich lipoprotein particles in the postprandial state.

Compound heterozygote for lipoprotein lipase deficiency: Ser----Thr244 and transition in 3' splice site of intron 2 (AG----AA) in the lipoprotein lipase gene.

Cloning and sequencing of translated exons and intron-exon boundaries of the lipoprotein lipase gene in a patient of French descent who has the chylomicronemia syndrome revealed that he was a compound heterozygote for two nucleotide substitutions. One (TCC----ACC) leads to an amino acid substitution (Ser----Thr244), while the other alters the 3' splice site of intron 2 (AG----AA). The functional significance of the Thr244 amino acid substitution was established by in vitro expression in cultured mammalian cells.

Phenotypic expression of heterozygous lipoprotein lipase deficiency in the extended pedigree of a proband homozygous for a missense mutation.

Familial lipoprotein lipase (LPL) deficiency is a rare genetic disorder accompanied by well-characterized manifestations. The phenotypic expression of heterozygous LPL deficiency has not been so clearly defined. We studied the pedigree of a proband known to be homozygous for a mutation resulting in nonfunctional LPL.

Lipoprotein lipase deficiency resulting from a nonsense mutation in exon 3 of the lipoprotein lipase gene.

In DNA from a male patient of German and Polish ancestry who has lipoprotein lipase deficiency, sequencing of all nine exons and intron-exon boundaries corresponding to the coding region of the lipoprotein lipase gene detected a C----T transition leading to the substitution of a stop signal for the codon that normally determines a glutamine at position 106 of the mature enzyme. Hybridization with allele-specific oligonucleotides at this position established that the patient was homozygous for this mutation. This mutation must lead to the synthesis of a sharply truncated protein, accounting for the enzymatic deficiency noted in the patient.

Missense mutation (Gly----Glu188) of human lipoprotein lipase imparting functional deficiency.

Cloning and sequencing of lipoprotein lipase (LPL) cDNA prepared from the adipose tissue of a patient with classical LPL deficiency revealed a G to A transition at nucleotide 818 in all sequenced clones, leading to the substitution of glutamic acid for glycine at residue 188 of the mature protein. Hybridization of genomic DNA with allele-specific oligonucleotides confirmed that the patient was homozygous for this mutation and revealed that carrier status for this mutation among relatives of the patient was significantly associated with hypertriglyceridemia. Assay of the patient's plasma for immunoreactive enzyme and activity demonstrated the presence of a circulating inactive enzyme protein, the concentration of which was further increased by injection of heparin.

Defective enzyme protein in lipoprotein lipase deficiency.

A monoclonal antibody to lipoprotein lipase (LPL) has been used in an enzyme-linked immunosorbent assay (ELISA) for LPL protein mass. Measurement of LPL immunoreactive mass in pre- and postheparin plasma distinguished three classes of abnormalities in patients with classical deficiency of lipoprotein lipase activity. The class I defect consisted of the absence of LPL immunoreactive homodimer in pre- and postheparin plasma compatible with a potential 'null allele'.

Detection and characterization of the heterozygote state for lipoprotein lipase deficiency.

Because there are no characteristic clinical or biochemical manifestations, the heterozygote state for lipoprotein lipase (LPL) deficiency has been difficult to detect. Measurements of postheparin plasma LPL activity and of LPL mass were performed in six families of probands with LPL deficiency to characterize the heterozygote state. LPL mass was measured in a sandwich enzyme-linked immunosorbent assay (ELISA) using a monoclonal antibody (5D2) that had been produced against bovine milk LPL.

Weight loss leads to a marked decrease in nonresting energy expenditure in ambulatory human subjects.

The extent to which the resting and nonresting components of 24-hour energy expenditure decrease after weight reduction has not been prospectively assessed in ambulatory, weight-stable, reduced-obese humans. Accordingly, 24-hour energy expenditure was estimated as the weight-stabilizing (+/- 50 g/d) daily caloric intake of a defined liquid diet in a cross-sectional study of ten reduced-obese subjects after a 23.2% +/- 9.

Relationship between lipoprotein lipase activity and plasma sex steroid level in obese women.

In obese women (n = 16) at their weight, fasting adipose tissue lipoprotein lipase (LPL) activity, obtained by elution with serum and heparin at 4 degrees and 37 degrees C, was inversely correlated to plasma estradiol levels (r = -0.724; P = 0.002) and (r = -0.